The goal is to develop a hybrid IPN network of polyvinyl acetate (PVAc) and ethylene-vinyl acetate (VAE). In this research work, the vinyl acetate (VAc)/ VAE hybrid emulsion and polyvinyl acetate emulsion (PVAc) were ...The goal is to develop a hybrid IPN network of polyvinyl acetate (PVAc) and ethylene-vinyl acetate (VAE). In this research work, the vinyl acetate (VAc)/ VAE hybrid emulsion and polyvinyl acetate emulsion (PVAc) were effectively synthesized. Emulsions with various characteristics have been developed by adjusting the weight ratios between the vinyl acetate monomer and the VAE component. The impacts on the mechanical, thermal, and physical properties of the films were investigated using tests for pencil hardness, tensile shear strength, pH, contact angle measurement, differential scanning calorimetry (DSC), and viscosity. When 5.0 weight percent VAE was added, the tensile shear strength in dry conditions decreased by 18.75% after a 24-hour bonding period, the heat resistance decreased by 26.29% (as per WATT 91) and the tensile shear strength decreased by approximately 36.52% in wet conditions (per EN 204). The pristine sample’s results were also confirmed by the contact angle test. The interpenetrating network (IPN) formation in hybrid PVAc emulsion as primary bonds does not directly attach to PVAc and VAE chains. The addition of VAE reduced the mechanical properties (at dry conditions) and heat resistance as per WATT 91. Contact angle analysis demonstrated that PVAc adhesives containing VAE had increased water resistance when compared to conventional PVA stabilised PVAc homopolymer-based adhesives. When compared to virgin PVAc Homo, the water resistance of the PVAc emulsion polymerization was enhanced by the addition of VAE.展开更多
Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate ...Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate the localization of IFR in the EVA matrix. Localizations in which IFR was dispersed in the PA6phase or in the EVA phase were prepared. The effect of the localization of IFR on the flame retardancy of EVA was investigated. The limited oxygen index (LOI), vertical burning (UL 94) and cone calorimeter test (CCT)showed that the localization of IFR in the EVA matrix exhibited a remarkable influence on the flame retardancy.Compared with EVA/IFR, a weak improvement in the flame retardancy was observed in the EVA/PA6/IFR blend withthe localization of IFR in the PA6 phase. When IFR was regulated from the PA6 phase to the EVA matrix,a remarkable increase in the flame retardancy was exhibited. The LOI was increased from 27.8%to 32.7%, and the UL 94 vertical rating was increased from V-2 to V-0. Moreover, an approximately 41.36%decrease in the peak heat release rate was exhibited. A continuous and compact intumescent charring layer that formed in the blends with the localization of IFR in the EVA matrix should be responsible for its excellent flame retardancy.展开更多
Carbon nanotube (CNT) has remarkable piezoresistive properties,which makes its extremely sensitive to the mechanical force. In this study,the CNT yarn with the strength of 90 MPa and the strain sensing gage factor of ...Carbon nanotube (CNT) has remarkable piezoresistive properties,which makes its extremely sensitive to the mechanical force. In this study,the CNT yarn with the strength of 90 MPa and the strain sensing gage factor of 1.75 was selected and embedded into the ethylene vinyl acetate (EVA) elastomer as a sensing material.By measuring the electric resistance changing under the stretching,bending,longitudinally and transversely compressing of the CNT embedded EVA, the resistance changing curves and their linear correlations were obtained and analyzed. The result shows that the gage factor under the tensile test is the highest( 2.51),which is higher than the original value of CNT yarn (1.75). The gage factors of the CNT yarn embedded into EVA elastomer under bending and longitudinal and transverse compression are 2.29,1.55 and 0.79,respectively.展开更多
The discarded feathers / ethylene vinyl acetate copolymer( EVA) thermoplastic composite materials was obtained with discarded feathers as reinforced material and EVA powders as matrix material by hot pressing method. ...The discarded feathers / ethylene vinyl acetate copolymer( EVA) thermoplastic composite materials was obtained with discarded feathers as reinforced material and EVA powders as matrix material by hot pressing method. Sound absorption properties were studied by changing mass ratio of discarded feathers and EVA,thickness of composite materials,hot pressing pressure and hot pressing temperature. It was found that the sound absorption properties of composite materials were good when the mass ratio of discarded feathers and EVA was 1: 1,thickness of composite materials was 30 mm,hot pressing pressure was 8 MPa,and hot pressing temperature was 80 ℃. Under the optimum conditions,the effect of composite density on sound absorption property was analyzed. In a certain range,the sound absorption property was enhanced with the decrease of the composite density.When the composite density was 0. 1g /cm^3, the maximum absorption coefficient was 0.96. Finally,the capillary theory was used to calculate the maximum sound absorption coefficient of discarded feathers / EVA thermoplastic composite materials. The good agreements of experimental results and calculated results proved the validity of the theoretical models.展开更多
Membranes were fabricated with high-density polyethylene (HDPE) and ethylene vinyl acetate (EVA) blend through thermally induced phase separation and were then used for vacuum membrane distillation (VMD). The membrane...Membranes were fabricated with high-density polyethylene (HDPE) and ethylene vinyl acetate (EVA) blend through thermally induced phase separation and were then used for vacuum membrane distillation (VMD). The membranes were supported by non woven polyester fabric with a special cellular structure. Different membrane samples were obtained by adjusting the polymer concentration, HDPE/EVA weight ratio, and coagulation bath temperature. The membranes were characterized by scanning electron microscopy (SEM) analysis, contact angle test, and evaluation of porosity and pore size distribution. A series of VMD tests were conducted using aqueous NaCI solution (0.5 mol·L^-1) at a feed temperature of 65 ℃ and permeate side absolute pressure of 3 kPa. The membranes showed excellent performance in water permeation flux, salt rejection, and long-term sta-bility. The HDPE/EVA co-blending membranes exhibited the largest permeation flux of 23.87 kg·m^-2·h^-1, and benign salt rejection of ≥99.9%.展开更多
Sepiolite （S9, B10, B20, B40） and boehmite have been added to an intumecent flame retardant （IFR） system to produce the halogen-free and fire-resistant ethylene-vinyl acetate copolymer （EVM） rubber. The rubber c...Sepiolite （S9, B10, B20, B40） and boehmite have been added to an intumecent flame retardant （IFR） system to produce the halogen-free and fire-resistant ethylene-vinyl acetate copolymer （EVM） rubber. The rubber contains ammonium polyphosphate （APP） as acid source, double pentaerythritol （D-PER） as carbon source and melamine （MN） as gas source. The effects of nano-filler sepiolite and boehmite on the fire-resistant property of EVM rubber based on IFR system were investigated. The test results show that the system with nano-filler of sepiolite B10 has the best fire-resistant property. The process of smoke emission and thermal decomposition, the element composition of char surface and the micro morphology of intumecent char layer of the EVM IFR system with nano-filler were also studied by NBS chamber, thermogravimetric （TG） analysis, X- ray photoelectron spectroscopy （XPS） and scanning electron microscope （SEM）.展开更多
Surface texture of the mouthguard affects the sense of adaptation in the athlete and further affects hygiene. Therefore, finish polishing is extremely important. The aim of this study was to investigate the difference...Surface texture of the mouthguard affects the sense of adaptation in the athlete and further affects hygiene. Therefore, finish polishing is extremely important. The aim of this study was to investigate the difference in the surface roughness after finishing polishing of ethylene-vinyl-acetate (EVA) sheets and after application of the finishing liquid, and to evaluate its effectiveness. Total of 48 specimens of EVA (3 × 3 mm) were divided into 4 groups according to polishing condition (control = unpolished;condition A = Robinson-brush;condition B = Lisko-Fine, and condition C = Mouthguard-wheel). Polishing was performed at low speed by using a straight headpiece. The rotation speeds were 5000, 4000 and 6000 rpm for condition A, B, and C, respectively. Next, a finishing liquid was applied to each specimen. For application, a cotton swab was used, and it was applied by three reciprocations. A non-contact surface shape measuring machine was used for measuring surface roughness;the measurement range is 1.65 mm and the resolution is 0.01 nm. The arithmetic average height (Sa) was measured. The differences in the surface roughness before and 15 min after the application of the finishing liquid were analyzed by two-way analysis of variance and Bonferroni’s multiple comparison tests. Surface roughness of the specimen before application became coarse in the order of control, condition C, B and A, and Sa was about 0.20, 1.98, 2.92, and 4.71 μm, respectively. The degree of reduction in roughness was about 1.0 μm or more than each polished state in conditions A and B. Condition C was not significantly different before and after application. No significant difference was observed between condition B and C after application. The results of this study showed that the surface roughness decreased due to the application of the finishing liquid when the surface roughness after finish polishing was about 2.0 μm or more.展开更多
Surface texture of the mouthguard affects the sense of adaptation in the athlete and further affects hygiene. The aim of this study was to investigate the changes over time in surface roughness after finish polishing ...Surface texture of the mouthguard affects the sense of adaptation in the athlete and further affects hygiene. The aim of this study was to investigate the changes over time in surface roughness after finish polishing of ethylene vinyl acetate (EVA) sheets and before and after finishing liquid application, and to evaluate its effectiveness. Total of 160 specimens of EVA (3 × 3 mm) were divided into 4 groups according to polishing condition (control = unpolished;RB = Robinson-brush;LF = Lisko-Fine, and MW = Mouthguard-wheel). Polishing was performed at low speed by using a straight headpiece. The rotation speed was 5000, 4000 and 6000 rpm for RB, LF, and MW, respectively. Next, a finishing liquid was applied to each specimen. Changes over time in surface roughness before and after application of the finishing liquid were compared by a non-contact surface shape measuring machine. The arithmetic average height (Sa) was measured. The measurement time points were before application, immediately after application, and at 5, 10, and 15 min after application. The changes over time of the surface roughness of the sheet before and after application of the finishing liquid were analyzed by two-way analysis of variance and Bonferroni’s multiple comparison tests. Surface roughness of the specimen before application became coarse in the order of control;MW, LF and RB, and Sa were about 0.21 μm, 2.03 μm, 2.94 μm, and 4.72 μm, respectively. That showed the same order after finishing liquid application. Significant decrease in Sa for RB and LF were seen at 10 min after application and at 5 min after application, respectively. Sa of MW was not significantly different before and after application. The results of this study showed that a lubricity of about 1.0 μm increases within 5 - 10 min of application of finishing liquid, but in cases where polishing was performed to about 2.0 μm;the application of finishing liquid has no ef-fect.展开更多
文摘The goal is to develop a hybrid IPN network of polyvinyl acetate (PVAc) and ethylene-vinyl acetate (VAE). In this research work, the vinyl acetate (VAc)/ VAE hybrid emulsion and polyvinyl acetate emulsion (PVAc) were effectively synthesized. Emulsions with various characteristics have been developed by adjusting the weight ratios between the vinyl acetate monomer and the VAE component. The impacts on the mechanical, thermal, and physical properties of the films were investigated using tests for pencil hardness, tensile shear strength, pH, contact angle measurement, differential scanning calorimetry (DSC), and viscosity. When 5.0 weight percent VAE was added, the tensile shear strength in dry conditions decreased by 18.75% after a 24-hour bonding period, the heat resistance decreased by 26.29% (as per WATT 91) and the tensile shear strength decreased by approximately 36.52% in wet conditions (per EN 204). The pristine sample’s results were also confirmed by the contact angle test. The interpenetrating network (IPN) formation in hybrid PVAc emulsion as primary bonds does not directly attach to PVAc and VAE chains. The addition of VAE reduced the mechanical properties (at dry conditions) and heat resistance as per WATT 91. Contact angle analysis demonstrated that PVAc adhesives containing VAE had increased water resistance when compared to conventional PVA stabilised PVAc homopolymer-based adhesives. When compared to virgin PVAc Homo, the water resistance of the PVAc emulsion polymerization was enhanced by the addition of VAE.
基金the National Natural Science Foundation of China (No.51673059)the Science and Technology Planning Project of Henan Province (No. 212102210636)the Opening Project of Jiangxi Province Key Laboratory of Polymer Micro/Nano Manufacturing and Devices (East China University of Technology)。
文摘Polyamide 6 (PA6) was employed as a charring agent of intumescent flame retardant (IFR) to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA). Different processing procedures were used to regulate the localization of IFR in the EVA matrix. Localizations in which IFR was dispersed in the PA6phase or in the EVA phase were prepared. The effect of the localization of IFR on the flame retardancy of EVA was investigated. The limited oxygen index (LOI), vertical burning (UL 94) and cone calorimeter test (CCT)showed that the localization of IFR in the EVA matrix exhibited a remarkable influence on the flame retardancy.Compared with EVA/IFR, a weak improvement in the flame retardancy was observed in the EVA/PA6/IFR blend withthe localization of IFR in the PA6 phase. When IFR was regulated from the PA6 phase to the EVA matrix,a remarkable increase in the flame retardancy was exhibited. The LOI was increased from 27.8%to 32.7%, and the UL 94 vertical rating was increased from V-2 to V-0. Moreover, an approximately 41.36%decrease in the peak heat release rate was exhibited. A continuous and compact intumescent charring layer that formed in the blends with the localization of IFR in the EVA matrix should be responsible for its excellent flame retardancy.
基金National Natural Science Foundations of China(Nos.51303025,51503120)Shanghai Science and Technology Committee,China(No.14YF1409600)+2 种基金Shanghai Municipal Education Commission,China(No.ZZgcd14016)Fundamental Research Funds for the Central Universities,ChinaDonghua University Distinguished Young Professor Program,China
文摘Carbon nanotube (CNT) has remarkable piezoresistive properties,which makes its extremely sensitive to the mechanical force. In this study,the CNT yarn with the strength of 90 MPa and the strain sensing gage factor of 1.75 was selected and embedded into the ethylene vinyl acetate (EVA) elastomer as a sensing material.By measuring the electric resistance changing under the stretching,bending,longitudinally and transversely compressing of the CNT embedded EVA, the resistance changing curves and their linear correlations were obtained and analyzed. The result shows that the gage factor under the tensile test is the highest( 2.51),which is higher than the original value of CNT yarn (1.75). The gage factors of the CNT yarn embedded into EVA elastomer under bending and longitudinal and transverse compression are 2.29,1.55 and 0.79,respectively.
文摘The discarded feathers / ethylene vinyl acetate copolymer( EVA) thermoplastic composite materials was obtained with discarded feathers as reinforced material and EVA powders as matrix material by hot pressing method. Sound absorption properties were studied by changing mass ratio of discarded feathers and EVA,thickness of composite materials,hot pressing pressure and hot pressing temperature. It was found that the sound absorption properties of composite materials were good when the mass ratio of discarded feathers and EVA was 1: 1,thickness of composite materials was 30 mm,hot pressing pressure was 8 MPa,and hot pressing temperature was 80 ℃. Under the optimum conditions,the effect of composite density on sound absorption property was analyzed. In a certain range,the sound absorption property was enhanced with the decrease of the composite density.When the composite density was 0. 1g /cm^3, the maximum absorption coefficient was 0.96. Finally,the capillary theory was used to calculate the maximum sound absorption coefficient of discarded feathers / EVA thermoplastic composite materials. The good agreements of experimental results and calculated results proved the validity of the theoretical models.
基金Supported by the Natural Science Foundation of Tianjin(18JCZDJC37200)the State Key Laboratory of Separation Membranes and Membrane Processes of Tianjin Polytechnic University(M2-201610)+2 种基金the Tianjin higher school innovation team training program(TD13-5008)the Yangtze Scholars and Innovative Research Team in University(IRT-17R81)the Innovative Research Team of Tianjin Municipal Education Commission(TD12-5004)
文摘Membranes were fabricated with high-density polyethylene (HDPE) and ethylene vinyl acetate (EVA) blend through thermally induced phase separation and were then used for vacuum membrane distillation (VMD). The membranes were supported by non woven polyester fabric with a special cellular structure. Different membrane samples were obtained by adjusting the polymer concentration, HDPE/EVA weight ratio, and coagulation bath temperature. The membranes were characterized by scanning electron microscopy (SEM) analysis, contact angle test, and evaluation of porosity and pore size distribution. A series of VMD tests were conducted using aqueous NaCI solution (0.5 mol·L^-1) at a feed temperature of 65 ℃ and permeate side absolute pressure of 3 kPa. The membranes showed excellent performance in water permeation flux, salt rejection, and long-term sta-bility. The HDPE/EVA co-blending membranes exhibited the largest permeation flux of 23.87 kg·m^-2·h^-1, and benign salt rejection of ≥99.9%.
基金Sponsored by Project in National Key Technology R&D Program(2006BAE03B05-2)
文摘Sepiolite （S9, B10, B20, B40） and boehmite have been added to an intumecent flame retardant （IFR） system to produce the halogen-free and fire-resistant ethylene-vinyl acetate copolymer （EVM） rubber. The rubber contains ammonium polyphosphate （APP） as acid source, double pentaerythritol （D-PER） as carbon source and melamine （MN） as gas source. The effects of nano-filler sepiolite and boehmite on the fire-resistant property of EVM rubber based on IFR system were investigated. The test results show that the system with nano-filler of sepiolite B10 has the best fire-resistant property. The process of smoke emission and thermal decomposition, the element composition of char surface and the micro morphology of intumecent char layer of the EVM IFR system with nano-filler were also studied by NBS chamber, thermogravimetric （TG） analysis, X- ray photoelectron spectroscopy （XPS） and scanning electron microscope （SEM）.
文摘Surface texture of the mouthguard affects the sense of adaptation in the athlete and further affects hygiene. Therefore, finish polishing is extremely important. The aim of this study was to investigate the difference in the surface roughness after finishing polishing of ethylene-vinyl-acetate (EVA) sheets and after application of the finishing liquid, and to evaluate its effectiveness. Total of 48 specimens of EVA (3 × 3 mm) were divided into 4 groups according to polishing condition (control = unpolished;condition A = Robinson-brush;condition B = Lisko-Fine, and condition C = Mouthguard-wheel). Polishing was performed at low speed by using a straight headpiece. The rotation speeds were 5000, 4000 and 6000 rpm for condition A, B, and C, respectively. Next, a finishing liquid was applied to each specimen. For application, a cotton swab was used, and it was applied by three reciprocations. A non-contact surface shape measuring machine was used for measuring surface roughness;the measurement range is 1.65 mm and the resolution is 0.01 nm. The arithmetic average height (Sa) was measured. The differences in the surface roughness before and 15 min after the application of the finishing liquid were analyzed by two-way analysis of variance and Bonferroni’s multiple comparison tests. Surface roughness of the specimen before application became coarse in the order of control, condition C, B and A, and Sa was about 0.20, 1.98, 2.92, and 4.71 μm, respectively. The degree of reduction in roughness was about 1.0 μm or more than each polished state in conditions A and B. Condition C was not significantly different before and after application. No significant difference was observed between condition B and C after application. The results of this study showed that the surface roughness decreased due to the application of the finishing liquid when the surface roughness after finish polishing was about 2.0 μm or more.
文摘Surface texture of the mouthguard affects the sense of adaptation in the athlete and further affects hygiene. The aim of this study was to investigate the changes over time in surface roughness after finish polishing of ethylene vinyl acetate (EVA) sheets and before and after finishing liquid application, and to evaluate its effectiveness. Total of 160 specimens of EVA (3 × 3 mm) were divided into 4 groups according to polishing condition (control = unpolished;RB = Robinson-brush;LF = Lisko-Fine, and MW = Mouthguard-wheel). Polishing was performed at low speed by using a straight headpiece. The rotation speed was 5000, 4000 and 6000 rpm for RB, LF, and MW, respectively. Next, a finishing liquid was applied to each specimen. Changes over time in surface roughness before and after application of the finishing liquid were compared by a non-contact surface shape measuring machine. The arithmetic average height (Sa) was measured. The measurement time points were before application, immediately after application, and at 5, 10, and 15 min after application. The changes over time of the surface roughness of the sheet before and after application of the finishing liquid were analyzed by two-way analysis of variance and Bonferroni’s multiple comparison tests. Surface roughness of the specimen before application became coarse in the order of control;MW, LF and RB, and Sa were about 0.21 μm, 2.03 μm, 2.94 μm, and 4.72 μm, respectively. That showed the same order after finishing liquid application. Significant decrease in Sa for RB and LF were seen at 10 min after application and at 5 min after application, respectively. Sa of MW was not significantly different before and after application. The results of this study showed that a lubricity of about 1.0 μm increases within 5 - 10 min of application of finishing liquid, but in cases where polishing was performed to about 2.0 μm;the application of finishing liquid has no ef-fect.
